Drawing ruthenium and alloys thereof to wire



United States Patent Office 3,528,862 Patented Sept. 15 1970 3,528,862 DRAWING RUTHENIUM AND ALLOYS THEREOF T WIRE 'Michael William Jones, Southall, Brian Taylor, London,

and Michael David Taylor, Stanmore, England, assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed June 19, 1968, Ser. No. 738,126 Claims priority, application Great Britain, July 10, 1967, 31,676/67 Int. Cl. C22f 1/14 US. Cl. 148-115 6 Claims ABSTRACT OF THE DISCLOSURE Improved results in drawing ruthenium or ruthenium alloy wire are obtained with new process involving special control of die temperature. The ruthenium is preheated to a temperature of about 1000 C. to about 1300 C. in a non-oxidizing atmosphere and subsequently drawn through a wire drawing die at a temperature of 900 C. to 1050 C.

The present invention relates to the art of wire drawing and more particularly to processes for drawing wire made of ruthenium or ruthenium-rich alloys.

It is well known that the refractory metal ruthenium is normally produced as a powder by the reduction of a salt or compound of the element. When the metal is required in a consolidated form the powder is preferably compacted and sintered by conventional powder-metallurgical techniques. The resultant metal, however, is usually difiicult to work and the workability can be improved by alloying it with from 0.1%, or 0.25%, to 25% rhenium by powder-metallurgical methods, e.g., as described in U.S. Pat. No. 3,362,799.

Ruthenium or a ruthenium-rich alloy is sometimes required as wire, e.g., for spark plug electrodes and thermocouples. Hitherto this has been produced by hot-drawing the metal or alloy through a die made of tungsten carbide in a cobalt or similar matrix or of other sintered hard metal, which is heated to as high a temperature as is practicable, e.g., to about 1200 C. Such processes however have the great disadvantages that only a very small reduction can be effected in each pass, the surface rfinish of the wire is poor due to breakdown of the lubricant, the wear on the die is very great and the yield of satisfactory material is low. Insofar as We are aware there was not heretofore known any process for drawing ruthenium wire that was entirely successful when carried into practice commercially on an industrial scale.

There has now been discovered a new process for drawing ruthenium wire that achieves improved results, including a good surface finish, and enables accomplishing greater cross-sectional reductions per pass during drawing.

It is an object of the present invention to provide a method of processing ruthenium and certain rutheniumrich alloys into wire.

Other objects and advantages of the invention will become apparent from the following description.

Generally speaking, the present invention contemplates a process comprising drawing a ruthenium-rich metal, which can be commercially pure ruthenium or a ruthenium alloy containing at least 90% ruthenium, through a die of hard metal that is maintained at a temperature of 900 C. to 1050 C. Below 900 C., the temperature of the die is too low and the wire splinters, thus giving an undesirable surface. Above 1050 C. the wear on the throat of the die is excessive and the finished size of the wire is very difficult, if not impossible, to control. Thus, the present invention involves the discovery that ruthenium is more readily hot drawn to wire when the temperature of the drawing die is relatively low and is controlled within narrow limits of 900 C. to 1050 C., advantageously 950 C.

For drawing in accordance with the present process the ruthenium, which is usually in the form of rod, is preheated to a temperature of about 1000 C. to about 1300 C., advantageously within the range of 1150" C. to 1250 C. This preheating may be done in an electric-resistance furnace and is advantageously done in a nonoxidizing atmosphere, such as an inert or reducing gas. When wire is drawn in accordance with the invention the hot die can be substantially enclosed in a small electric-resistance tube furnace containing an inert or reducing, and thus nonoxidizing, atmosphere, e.g., an atmosphere of hydrogen. It is essential to lubricate the wire and it is advantageous to use graphite for the lubricant in the present process. However, any hot drawing lubricant that is not harmful to ruthenium will usually suffice. It is highly de sirable to prevent oxidation of the wire when it emerges from the die and it is also advantageous to chill the wire at this stage to obtain adequate strength in the wire at that zone in order to enable the drawing force to be maintained without breaking the wire. These objects of preventing undue oxidation and obtaining adequate strength can be accomplished simultaneously by quenching the emerging wire with a water jet, which ensures that it falls to a temperature at which oxidation will not take place and which also provides a blanket of steam around the die outlet and so assists in preventing oxidation. The water jet should be as close to the die as possible without impinging directly upon it. It will, of course, be understood that other harmless quenching fluids that are volatilizable into a protective atmosphere can also be employed for these purposes.

Alloys of ruthenium which are processed in accordance with the invention include ruthenium powder metallurgical alloys containing 0.1% or 0.25% or more rhenium, e.g., 2% rhenium. For obtaining good results in drawing ruthenium-rhenium wire according to the process of the invention the rhenium content is controlled to amounts not greater than about 10%, e.g., 0.1% to 10% rhenium. All alloy composition percentages set forth herein are by weight. Ruthenium-rhenium alloy products, e.g., rods, that are suitable as wire drawing stock for the process of the invention can be produced by the method described in Us. Pat. No. 3,362,799. Advantageously the ruthenium-rich metals drawn in the process of the invention contain at least about ruthenium.

Wire-drawing dies for the present process are of heatresistant hard metal, e.g., sintered metals such as cobaltbonded tungsten carbide. Another satisfactory metal for the dies is chromium carbide. It is to be understood that any other hard metal carbide of sufficient wear resistance may also be used and that certain ceramic dies such as those of alumina or similar ceramics may offer advantages.

For the purpose of giving those skilled in the art a better understanding and appreciation of the advantages of the invention the following illustrative examples are given:

EXAMPLE I Commercially pure ruthenium powder containing at least about 99.9% ruthenium and very small amounts of impurities, e.g., 0.001% palladium, 0.03% osmium, 0.01% iron, 0.002% nickel, and of particle sizes passing through a 200 British Standard Screen (BSS) mesh sieve was pressed isostatically in a flexible bag at a pressure of 25 long tons (2240 pounds) per square inch. This pressing produced a right cylindrical. compact of 3-inches length and 0.5-inch diameter. The thus-produced compact was sintered at 1450 C. for 8 hours in vacuo to form a right cylindrical ingot. The sintered ingot was swaged at 1500 C. to rod of 0.2-inch diameter and, after being centerless ground to remove surface defects, the swaged and ground rod was preheated to 1200 C. and was then drawn at about this temperature in 31 passes to 0.046-inch around the wire, thus inhibiting oxidation and rapidly increasing the wire strength. Good surface finishes were obtained on the thus-drawn wires produced in the present Examples 2 through 7. It is to be particularly noted that advantageously good ductility, and also a high rediameter through tungsten carbide dies at a die tempera- 5 duction of area without intermediate annealing during ture of 950 C. At each pass a reduction in area of about drawing, was obtained in Example 4 which utilized an- 15% was elfected and after each reduction of about 30%, ncaling by heat treatment B before and after drawing.

i.e., 2 passes, the wire was flash-annealed in an induction In contrast to the good surface finish results obtained furnace in an atmosphere of hydrogen and 90% 10 with Examples 1 through 7, detrimental splintering on the nitrogen for 10 seconds at 1800 C. For each pass the Wire Surface was encountered when swaged and centerless wire was lubricated by an aqueous suspension of graphite. ground rod of an alloy containing 2% rhenium and bal- When thus drawn to 0.046-inch diameter the ruthenium ance ruthenium was preheated to 1200 C. and drawn wire produced in this example of the invention was of with the die at a temperature of 800 C. (which die temgood quality with a highly satisfactory surface finish. perature is not in accordance with the invention) and When, in a process not in accordance with the invenwith practices of annealing, drawing speed and lubrication tion, another portion of the same ruthenium rod was which were satisfactory in the foregoing examples of the drawn through tungsten carbide dies under the same coninvention. Also, when Ru-2% Re wire was drawn acditions except with the die temperature at 1200 C. and cording to good general practices for the foregoing exa preheat temperature of 1500 C., 70 passes were reamples but with the wire preheated to 1500 C. and the quired to achieve a diameter of 0.046 inch and the surface die preheated to 1200 C. about 60 to 70 passes, which is finish wasmetallurgically inferior to the wire drawn in excessively high, and a greater number of anneals were Example I. Ne dless to say, the reductions obtainable with required for drawing down to the diameters obtained in the die at 1200 C. were much less than the reductions Examples 2 through 7 and die wear was increased by a accomplished with the process of the invention. The econfactor of ten under these preheat and die temperature conomies in die wear and labor achieved by the invention are ditions, which are not in accordance with the invention. substantial. For example, the die wear was reduced by a The present invention is particularly applicable to the factor of ten. Moreover, better quality is obtained with production of ruthenium wire for use in sparking plug the process of the invention. electrodes and thermocouples.

Particulars pertaining to further examples of satisfac- Although the present invention has been described in tory production of wire utilizing the process of the invenconjunction with preferred embodiments, it is to be undertion are set forth in the following table. stood that modifications and variations may be resorted TABLE Bend Example Rod stock Number of Anncal Number of Final wire ductility, No. Metal dia., inch passes H.T anneals dia., inch degrees 2 Bil-2% Rem. 0.157 30 A 8 0.060 32 0.177 10 B 0 0. 000 31 0.177 29 B 0 0. 046 30 0.169 10 A 5 0.060 29 0.060 7 A 1 0. 040 19 7 Ru-2% Re 0.109 23 B 2 0.060

Metal-Ru-2% Re refers to alloy of 2% rhenium and balance ruthenium.

Rod stock dia.-Diameter of red at start of drawing.

Anneal H.T.AAnnealing heat treatment, during wire drawing, of flash annealing by induction heating to about 1,800 C. for 5 to 10 seconds in a nitrogen-10% hydrogen atmosphere.

Anneal HEB-Annealing heat treatment, during wire drawing, by holding in a resistance furnace at 1,500 C. in a hydrogen atmosphere.

Number of anneals-N umber of anneals dun'ng wire drawing. Final wire dia.-Diarneter of wire at finish of drawing.

Bend ductility-Angl0 of bend to crack finally annealed Wire over 10 mm. diameter.

In connection with the foregoing Examples 2 through 7, it is noted that for each of these examples the wire was preheated to 1200 C. and drawn through tungsten carbide dies that were heated to 950 C. In preparing the drawing stock, powders of the metals to be drawn were consolidated by compaction and sintering and the sintered compacts were then worked to rod by forging and swaging. Before drawing, the swaged rods were centerless ground, generally reducing the diameter about 0.02 inch, and were then annealed using the same heat treatment that was to be applied for intermediate annealing, if any. Drawing lubrication was applied with semicolloidal graphite layers that were baked onto the rods or wires before each pass. Additionally, the bore of the die was impregnated with graphite lubricant. The wire was drawn at a speed of about 30 inches per minute with the die in a resistance furnace wherein a hydrogen atmosphere was maintained. A water jet was directed onto the hot wire where it emerged from the furnace so as to quench the Wire below red heat and provide a steam atmosphere to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. In a process of hot drawing a ruthenium-rich metal containing at least about ruthenium through a hard metal die, the improvement comprising preheating said ruthenium-rich metal to a temperature of about 1000 C. to about 1300 C. in a nonoxidizing atmosphere and, while protecting said preheated ruthenium-rich metal from oxidation, drawing the hot ruthenium-rich metal through the wire drawing die at a die temperature of 900 C. to 1050 C.

2. A process as set forth in claim 1 wherein the preheating temperature of the ruthenium-rich metal is 1150 C. to 1250 C.

3. A process as set forth in claim 1 comprising, at about the time the wire emerges from the die, chilling 5 6 the drawn wire and simultaneously providing a nonoxidiz- References Cited ing atmosphere around the emerging wire. UNITED STATES PATENTS 4. A process as set forth in claim 1 comprising directing a water jet onto the wire at about the time the wire 3,124,657 7/1965 J nes at al. l 148-11.5 X emerges f the r ,3 2,799 1/1968 Betterl ge et a 75172 X 5. A process as set forth in claim 1 wherein the rutheni- 0 um-rich metal is commercially pure ruthenium.

6. A process as set forth in claim 1 wherein the U s c] X R ruthenium-rich metal is an alloy containing 0.1% to about 10% rhenium and balance essentially ruthenium. 2 0

CHARLES N. LOVELL, Primary Examiner 33 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,528,862 Dated ept. 5, 97

MICHAEL WILLIAM JONES, BRIAN TAYLOR 8c InVBn )l/[TCHAFIT. DAVTT) 'TAYLOR Patent No.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[ Column l, between lines 32 and 55, in last column of Table, under "Bend ductility, degrees,

for "32 read -19 3 23 3O 33 29 2O l9 l9 Signed and sealed this 2nd day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

